The invention relates to the field of oil burner control systems and more particularly to electronic control circuits having fail safe capabilities with a circuit breaker activated by the secondary of the control circuit.
In prior art systems, specifically represented by: Lenski, U.S. Pat. No. 3,770,365; the application of Lenski entitled, "Burner Control" Ser. No. 362,387 filed on May 21, 1973; and the application of MacAskill entitled "Burner Control System With Primary Safety Switch," which are all assigned to the assignee of this application, utilize either an electromechanical safety switch in the secondary portion of the control circuit for the purpose of disconnecting the burner motor when, after call for heat by the thermostat, a flame is not detected at the burner within certain time limits; or, in the MacAskill application, utilize a safety switch in the primary of the burner control circuit for the above purpose in addition to disconnecting the motor in the event the triac controlling the application to the line voltage to the motor should become shorted. The application of MacAskill also uses an electronic timing circuit in the secondary for governing the time between a call for heat by the thermostat and the switching off of the burner due to a failure to detect a flame at the burner.
Although the application of MacAskill provided substantial improvements over the other systems, the utilization of the electronic timing circuitry, however, tended to add complexity and cost to the burner control system.